JP5146756B2 - Radioactive waste burying and disposal facility and radioactive waste burying method - Google Patents

Description

  The present invention relates to a radioactive waste embedding disposal facility and a radioactive waste embedding method.

  Radioactive waste generated from the use of nuclear power at nuclear power plants will be disposed of after being treated in an appropriate manner to ensure safe management so as not to have a significant impact on the human environment. It has become. For example, high-level radioactive waste (high-level radioactive waste) remaining after separation of useful materials such as uranium and plutonium from spent fuel by reprocessing is cooled for 30 to 50 years after solidifying with glass. For storage, and then buried deep underground.

  As shown in FIG. 1, an embedding disposal facility (underground facility) for embedding radioactive waste solidified with glass (a vitrified body 1) is a waste body 3 (a vitrified body 1 is overpacked 2 (made of metal) from the ground facility. 1) and an access tunnel for transporting construction materials and the like, a disposal tunnel 4 for disposing a waste body, a disposal hole 5, and the like.

  As shown in FIG. 1, an embedding disposal facility in which the waste body 3 is buried vertically is excavated in the disposal hole 5 from the disposal tunnel 4 at regular intervals, and the waste body 3 is placed there, and the waste body 3 and the disposal hole The cushioning material 6 is filled in between.

  For example, a bentonite-based soil material in which bentonite and sand are mixed is used as the buffer material 6, and predetermined elasticity and water impermeability are exhibited by compacting the soil material. The buffer material 6 is also referred to as a water-impervious material, and reduces external force applied to the waste body 3 when an external force such as an earthquake is applied to deform the disposal tunnel 4 or the disposal hole 5 and also prevents the ingress of groundwater. It is like that.

  As the form of the cushioning material 6, a block type is being studied in addition to the on-site compaction type. As shown in FIG. 2, the block-type cushioning material 60 is composed of two types: a disk-shaped block-type cushioning material 61 and a donut-shaped block-type cushioning material 62 in which a hole for storing waste is formed in the center. After installing the disk-shaped block type buffer material 61 in the disposal hole 5, the waste body 3 is installed and the donut-shaped block type buffer material 62 is stacked, and then the disk-shaped block type buffer material 61 is again formed. As a result, the waste body 3 is accommodated inside the block-type cushioning material 60. Note that these may be assembled into smaller blocks (see, for example, Non-Patent Document 1).

  In addition, as shown in FIG. 3, by filling the gap between the block-type cushioning material 60 installed in the disposal hole 5 and the disposal hole 5 with a granular bentonite-based high-density solid (pellet-type cushioning material 7), A buried disposal facility in which a gap between the block-type cushioning material 60 and the disposal hole 5 is filled has been proposed. According to this buried disposal facility, even if the block-type cushioning material 60 is collapsed, the pellet-type cushioning material 7 exhibits the cushioning performance and the water shielding performance (for example, see Patent Document 1).

Japan Nuclear Power Environment Organization, “Technology and safety of geological disposal of high-level radioactive waste”, [online], [searched on August 1, 2008], Internet <URL: http: //www.numo.or. jp / siryou / gijyutsu / 4alldl / tr0401all.pdf> JP 2007-319732 A

However, when the salinity of the groundwater exuding from the surrounding rock mass of the disposal hole 5 is high, the block-type cushioning material 60 is collapsed by the groundwater entering the block-type cushioning material 60 as shown in FIG. Thus, a situation occurs in which the pellet type buffer material 7 cannot be filled in the gap between the block type buffer material 60 and the disposal hole 5. For example, a simulated buffer material having a volume of 100 cm ³ and an initial moisture saturation (volume ratio of moisture that fills the gap between materials) (Sr) of 47% is immersed in salt water having a salt concentration (NaCl) concentration of 4% for about 30 minutes. All collapse (see Fig. 5). If the salinity of the groundwater is low, even if the groundwater enters the block-type cushioning material 60, the block-type cushioning material 60 will not be destroyed immediately, so the gap between the block-type cushioning material 60 and the disposal hole 5 It is not necessary to consider the situation where the pellet type cushioning material 7 cannot be filled.

  The present invention has been made in view of the above, and even when the salinity of groundwater oozed out from the surrounding rock mass of the disposal hole is high, the pellet-type cushioning material is used before the block-type cushioning material collapses. An object of the present invention is to provide a radioactive waste embedding disposal facility and a radioactive waste embedding method capable of completing filling.

  In order to solve the above-described problems and achieve the object, the present invention includes a block-type cushioning material installed in a disposal hole in which a clay-based soil material mainly composed of bentonite is compacted and embedded with radioactive waste. In a radioactive waste embedding disposal facility that is filled between a disposal hole and a block-type cushioning material and has a granular pellet-type cushioning material mainly composed of bentonite, the block-type cushioning material is disposed in the disposal hole. Even if groundwater with high salinity oozes out, clay-based soil material with adjusted water saturation is compacted so that the form is maintained until the filling of the pellet-type buffer material is completed. .

  Moreover, the present invention is characterized in that, in the above invention, the water saturation of the clay-based soil material is 88% or more.

  In addition, the present invention provides a block-type cushioning material in which a clay-based soil material mainly composed of bentonite is compacted, and then installs the block-type cushioning material in a disposal hole for embedding radioactive waste. In the method of embedding radioactive waste in which the pellet-type buffer material containing bentonite as the main component is filled in the gap between the block-type buffer material and the pellet-type buffer material The clay-based soil material is compacted after adjusting the water saturation of the clay-based soil material so that the block-type cushioning material maintains its form until the filling is completed.

  The present invention is characterized in that, in the above invention, the water saturation of the clay-based soil material is adjusted to 88% or more.

  The block type buffer material of the radioactive waste embedding disposal facility according to the present invention has a moisture content so as to maintain its form until the filling of the pellet type buffer material is completed even if groundwater with a high salinity concentration oozes into the disposal hole. Since the clay-based soil material whose saturation is adjusted is compacted, the filling of the pellet-type cushioning material can be completed before the block-type cushioning material collapses.

  The method for embedding radioactive waste according to the present invention is a clay type so that the block-type cushioning material maintains its form until the filling of the pellet-type cushioning material is completed even when groundwater with a high salinity concentration oozes into the disposal hole. Since the clay-based soil material is compacted after adjusting the water saturation of the soil material, the filling of the pellet-type buffer material can be completed before the block-type buffer material collapses.

  DESCRIPTION OF EMBODIMENTS Embodiments of a radioactive waste embedding disposal facility and a radioactive waste embedding method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

FIG. 5 is a diagram showing the results of a salt water immersion test of simulated buffer materials having different initial water saturation levels. The simulated cushioning material used in this test is a mixture of bentonite and silica sand as an aggregate, and has the following specifications.
-The bentonite should use Na type bentonite.
・ For silica sand, use a mixture of silica sand No. 3 and silica sand No. 5 at a ratio of 1: 1.
・ The mixing ratio of bentonite and silica sand is 70% to 30%.
-The dry density of the simulated cushioning material is 1600 kg / m ³ .
The initial moisture saturation (Sr) of the simulated cushioning material is 0%, 47%, 67%, 88%, 97%.
Moreover, the salt content (NaCl) density | concentration of the salt water to immerse shall be 4% substantially the same as seawater.

  As shown in FIG. 5, the decay rate of the simulated cushioning material decreases as the initial water saturation (Sr) increases. For example, when the initial water saturation (Sr) becomes 88% or more, the form is maintained for about 90 minutes (for example, a state in which particles are not dropped even if particles are floated by diffusion).

  Based on this, the block-type cushioning material of the radioactive waste embedding disposal facility according to the present invention has the form until the filling of the pellet-type cushioning material is completed even if groundwater with a high salinity concentration oozes into the disposal hole. The clay-based soil material with adjusted water saturation (initial water saturation) Sr is compacted so as to maintain. For example, the water saturation (initial water saturation) Sr of the clay-based soil material is adjusted to 88% or more.

  Similarly, in the method for embedding radioactive waste according to the present invention, the block-type cushioning material maintains its form until the filling of the pellet-type cushioning material is completed even if groundwater with a high salinity concentration oozes into the disposal hole. As described above, after adjusting the water saturation of the clay-based soil material, the clay-based soil material is compacted to produce a block-type cushioning material. For example, a clay soil material whose moisture saturation (initial moisture saturation) Sr is adjusted to 88% or more is compacted.

(Embodiment)
A radioactive waste embedding disposal facility according to an embodiment of the present invention will be described. The radioactive waste embedding disposal facility according to the embodiment of the present invention is an embedding disposal facility referred to as a vertical waste disposal system, and, as shown in FIG. The waste body 3 is placed there, and the buffer material 6 is filled between the waste body 3 and the disposal hole 5.

  In the waste body 3, the vitrified body 1 in which radioactive waste is sealed is further sealed in a metal container called an overpack 2 (for example, an iron container having a thickness of about 200 mm). A buffer material 6 having a thickness of about 300 mm is filled between the first and second disposal holes.

  The buffer material 6 is intended to physically protect the waste body 3 and to suppress the migration of the radionuclide even after the confinement function of the overpack 2 is lost. Functions such as adsorption of dissolved nuclides and prevention of colloid migration are required.

  The cushioning material 6 filled between the waste body 3 and the disposal hole 5 in the present embodiment is composed of a block-type cushioning material 60 and a pellet-type cushioning material 7.

  There are two types of the block-type cushioning material 60: a disk-shaped block-type cushioning material 61 and a donut-shaped block-type cushioning material 62 in which a hole for storing waste is formed in the center. Water saturation (initial stage) is maintained so that even if groundwater with high water content (for example, groundwater having substantially the same salinity (4%) as seawater) starts to be maintained until the pellet-type cushioning material 7 is completely filled. It is configured by compacting a clay-based soil material with adjusted water content (Sr). For example, a clay soil material whose moisture saturation (initial moisture saturation) Sr is adjusted to 88% or more is compacted.

  The clay-based soil material is a clay-based soil material mainly composed of bentonite, and is composed of bentonite mixed with silica sand as an aggregate. More specifically, bentonite is Na-type bentonite, silica sand is a mixture of silica sand No. 3 and silica sand No. 5 in a ratio of 1: 1, and the mixing ratio of bentonite and silica sand is 70% to 30%. We use what we did.

  The pellet type buffer material 7 is a granular buffer material mainly composed of bentonite filled between the disposal hole 5 and the block type buffer material 60. The particle size of the pellet type buffer material 7 is, for example, 1 mm, 2 mm, or 4 mm.

  The block-type cushioning material 60 and the pellet-type cushioning material 7 are manufactured at a ground cushioning material manufacturing facility (factory).

  The manufacturing method of the block-type cushioning material 60 will be described more specifically based on FIGS. FIG. 6 is a process diagram showing the manufacturing procedure of the block-type cushioning material, and FIG. 7 is a schematic diagram showing the manufacturing procedure of the block-type cushioning material.

As shown in FIG. 6, clay-based soil materials (bentonite and silica sand) are kneaded at a predetermined moisture content. Thereafter, as shown in FIG. 7, carbon dioxide gas (C0 ₂ ) is blown to eliminate air in the material gap. Then, while evacuating, the clay-based soil material is press-compressed. Thereafter, the bottom plate is removed and the piston is pushed out, whereby the block-type cushioning material 60 having a predetermined moisture saturation (for example, 88% or more) is manufactured.

  In the radioactive waste embedding disposal facility described above, the block-shaped cushioning material 61 created at a predetermined moisture saturation in the cushioning material production facility (factory) on the ground is disposed in the disposal hole 5 with a disk-shaped block-shaped cushioning material 61. After the installation, the waste body 3 is installed and the donut-shaped block-type cushioning material 62 is stacked, and then the disk-shaped block-type cushioning material 61 is stacked again so that the waste body is placed inside the block-type cushioning material 60. 3 is stored.

  And the clearance gap between the block type buffer material 60 and the disposal hole 5 is filled by filling the granular pellet type buffer material 7 in the clearance gap between the block type buffer material 60 installed in the disposal hole 5 and the disposal hole 5.

  The block-type cushioning material 60 of the radioactive waste embedding disposal facility according to the above-described embodiment has a configuration until the filling of the pellet-type cushioning material 7 is completed even if groundwater with a high salt concentration starts to seep into the disposal hole 5. Since the clay-based soil material with the adjusted water saturation is compacted so as to be maintained, the filling of the pellet-type cushioning material 7 can be completed before the block-type cushioning material 60 collapses.

  Further, in the method for embedding radioactive waste according to the above-described embodiment, the block-type cushioning material 60 is in the form until the filling of the pellet-type cushioning material 7 is completed even when groundwater having a high salinity concentration oozes into the disposal hole 5. Since the clay-based soil material is compacted after adjusting the water saturation of the clay-based soil material so that the block-type buffer material 60 collapses, the filling of the pellet-type buffer material can be completed. .

It is a conceptual diagram which shows the burial disposal facility of radioactive waste. It is process drawing which shows the installation procedure of a block type shock absorbing material. It is a cross-sectional view which shows the burial disposal facility of radioactive waste. It is a cross-sectional view which shows the burial disposal facility of radioactive waste. It is a figure which shows the result of the salt water immersion test of the simulation buffer material from which initial stage water saturation differs. It is process drawing which showed the manufacture procedure of the block type buffer material. It is the schematic diagram which showed the manufacture procedure of the block type buffer material.

Explanation of symbols

1 Vitrified body 2 Overpack 3 Waste body (radioactive waste)
4 Disposal tunnel 5 Disposal hole 6 Buffer material 60 Block type buffer material 61 Disc-shaped block type buffer material 62 Donut-shaped block type buffer material 7 Pellet type buffer material

Claims (4)

Clay-based soil material mainly composed of bentonite is compacted, and it is filled between the block-type cushioning material installed in the disposal hole where the radioactive waste is buried and between the disposal hole and the block-type cushioning material. In a radioactive waste burial facility equipped with granular pellet type cushioning materials as components,
The block-type cushioning material is tightened with a clay-based soil material with adjusted water saturation so that the shape of the block-type cushioning material is maintained until the filling of the pellet-type cushioning material is completed even if groundwater with a high salinity concentration seeps into the disposal hole. A radioactive waste burial facility that is solidified.   2. The radioactive waste embedding disposal facility according to claim 1, wherein the water saturation of the clay-based soil material is 88% or more. After making block type buffer material compacted with clay-based soil material mainly composed of bentonite, block type buffer material is installed in the disposal hole where radioactive waste is buried, and then the disposal hole, block type buffer material and In the method of embedding radioactive waste in which a granular pellet type buffer material mainly composed of bentonite is filled in the gap between
After adjusting the water saturation of the clay-based soil material so that the block-type buffer material maintains its form until the filling of the pellet-type buffer material is completed even if groundwater with high salinity seeps into the disposal hole, A method for embedding radioactive waste characterized by compacting a soil material.   The method for embedding radioactive waste according to claim 3, wherein the water saturation of the clay-based soil material is adjusted to 88% or more.

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